Folding webs or articles which have a substantial extension in a length dimension along a fold line extending cross-directionally has since long been a challenge in a number of industry sectors, such as the textile sector, the hygiene or medical sectors, the packaging sectors, or the bookbinding/printing sectors.
Such cross-directional folds may be applied as such—so as to fold the web or piece or article for convenient packing. Folding of supple or delicate material, such as hosiery items, by means of a pivoting belt system has been described in U.S. Pat. No. 5,996,861. Cross-directional folding may also be a constructional feature and may impact the functionality of the article, such as in the case of disposable absorbent products, see e.g. EP-A-0254700, or in particular for so called “training pants”, see e.g. U.S. Pat. No. 6,726,792.
Creating CD folds in a continuous web for attaching other materials thereto has been described in EP-A-0974323. Therein, a rotating wheel is disclosed, with individual plates forming the outer shell contacting the web. The segments are rotatably mounted about the axis of a circular path such that upon rotation of the wheel the distances between two adjacent plates change as well as the circumferential velocities of the plates vary between a minimum and a maximum value. In the described embodiments, this is achieved by affixing the plates to extendible and pivotable arms, all of which are affixed and rotatably mounted in the centre of a second circle offset the first circle. When a continuous web is run over the wheel by being affixed to the plates, the web will form loops when the gaps between the plates narrow and these loops will be pulled straight again when the gaps widen. This process allows for particular process steps to be executed on the web, such as attaching stretched elastics to the zones contacting the plates, but not in the zones being folded away. Cross-directional folding may also be used when forming a closed structure such as a pant-type article by combining parts of a web of an article to each other as described for example in WO-A-97/28709 in the context of producing underwear such as pants from non-woven material, or in U.S. Pat. No. 6,062,444, describing an arrangement for folding surgical gowns, or in EP-A-01120054 relating to disposable coats.
In the area of packing, cross-directional folds are used in so called festooning processes, such as described in US-A-2002/0046549, wherein a strip of material is packed by being folded in a zigzag fashion by means of a reciprocating carriage. In U.S. Pat. No. 5,144,787 the packing of articles of varying dimensions is disclosed, using an elevator type package wrapping machine wherein a film is wrapped around the article by means of an underfolder.
A folding machine for tri-folding a paper web is disclosed in U.S. Pat. No. 5,165,671, using a cutter drum with saw blade, a folding drum with saw blade receivers and folding blades, first folding drum and folding blades. Folding is further an important process step in the printing and bookbinding industry, such as described in U.S. Pat. No. 6,428,260, disclosing a first and a second adhesive edge are folded around the spine of a book by means of L-shaped clamp. In U.S. Pat. No. 5,876,027 a sheet bundle folding apparatus is disclosed, causing a bundle of sheets to be rolled into a pair of fold rollers thereby folding the bundle of sheets. The apparatus is provided with a drive source for rotating the pair of fold rollers in a normal direction to roll in the bundle of sheets and in a reverse direction to return the rolled-in bundle of sheets.
In all such sectors, it is desirable to produce at high production speeds, and henceforth also high transfer speeds of the webs, however, it should be noted that the presently applied techniques of folding parts or pieces of a web rely generally on a free movement of an edge of the web material (such as the leading edge, or the folding edge), see e.g. U.S. Pat. No. 6,669,618, where a disposable diaper is CD-folded and the end sections of the article are folded one on the other and connected to each other by means of a slot and tab fastener system. Any free movement of a leading edge, however, has the risk of inducing large variations with regard to positioning, and this risk increases strongly with increasing production speed.
The web speed during such process steps can be reduced without impacting the output of the productions system by using a means for splitting the web path so as to allow parallel working on parts, or pieces or sections of the web. Such web path splitting means can be a rotating wheel, such as described in U.S. Pat. No. 6,656,312. However, also such mechanical solutions pose speed limitations, as the rotatably moving shell segments need to be properly controlled in their acceleration and deceleration phase.
Such mechanical approaches also imply difficulties, when—as is often the case—process flexibility with regard to varying dimensions, and in particular varying length dimensions of the articles is desired. Not only is the available maximum folding dimension limited by the hardware design, but also the dimensions of the unfolded part of the web, or piece or part thereof are fixed for one set of hardware. Henceforth, when different sizes are to be produced, the complete hardware of the rotating wheel has to be exchanged.
The present invention provides in one aspect a solution to these problems. However, it further provides solutions to web treatment problems, which are hitherto unresolved, or which have been addressed so far by processes not involving CD-folding. This aspect refers in particular to web treatment process steps, which require a certain process time and a very accurate relative positioning of certain sections of the web or of pieces or parts thereof to other sections of the web or pieces or parts thereof relative to other materials, such as may be another web material. In this aspect, the present invention is particularly suitable due to the very controlled movement of the web material. This is achieved by submitting different sections of the web materials to a web section speed differing from the overall web path speed in absolute value and/or in direction of movement. This can be realized by a combination of a web support means (such as vacuum belts), and a drive means for the web support means (such as programmable drives such as servo drives). A web path splitting means (such as rotatable drums or wheels looped into the web path) allows parallel working on several sections of the web or on several pieces or parts of the web.